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Demographic impacts on the foraging ...

Hassrick, Jason.

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Demographic impacts on the foraging ecology of northern elephant seals.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Demographic impacts on the foraging ecology of northern elephant seals./
Author:	Hassrick, Jason.
Description:	139 p.
Notes:	Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: .
Contained By:	Dissertation Abstracts International72-11B.
Subject:	Biology, Ecology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3471798
ISBN:	9781124836263

Demographic impacts on the foraging ecology of northern elephant seals.
Hassrick, Jason.

Demographic impacts on the foraging ecology of northern elephant seals. - 139 p.

Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: .

Thesis (Ph.D.)--University of California, Santa Cruz, 2011.

The range of foraging behaviors available to deep diving, air breathing marine vertebrates is constrained by their physiological capacity to breath-hold dive. In Chapter 1, I measured body oxygen stores (blood volume and muscle myoglobin) and diving behavior in adult female northern elephant seals ( Mirounga angustirostris) to investigate age-related effects on diving performance. Blood volume averaged 74.4 +/- 17.0 L in female elephant seals or 20.2 +/- 2.0% of body mass. Plasma volume averaged 32.2 +/- 7.8 L or 8.7 +/- 0.7% of body mass. Absolute plasma volume and blood volume increased independently with mass and age. Hematocrit decreased weakly with mass but did not vary with age. Muscle myoglobin concentration, while higher than previously reported (7.4 +/- 0.7 g%), did not vary with mass or age. Pregnancy status did not influence blood volume. Mean dive duration, a proxy for physiological demand, increased as a function of how long seals had been at sea, followed by mass and hematocrit. Strong effects of female body mass (range: 218--600 kg) on dive duration that were independent of oxygen stores suggest that larger females had lower diving metabolic rates. A tendency for dives to exceed calculated aerobic limits occurred more frequently later in the at-sea migration. These data suggest that individual physiological state variables and condition interact to determine breath-hold ability, and that both should be considered in life-history studies of foraging behavior.

ISBN: 9781124836263Subjects--Topical Terms:

1017726
Biology, Ecology.

Demographic impacts on the foraging ecology of northern elephant seals.
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020 $a 9781124836263
035 $a (UMI)AAI3471798
035 $a AAI3471798
040 $a UMI $c UMI
100 1 $a Hassrick, Jason. $3 1683800
245 1 0 $a Demographic impacts on the foraging ecology of northern elephant seals.
300 $a 139 p.
500 $a Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: .
500 $a Adviser: Daniel P. Costa.
502 $a Thesis (Ph.D.)--University of California, Santa Cruz, 2011.
520 $a The range of foraging behaviors available to deep diving, air breathing marine vertebrates is constrained by their physiological capacity to breath-hold dive. In Chapter 1, I measured body oxygen stores (blood volume and muscle myoglobin) and diving behavior in adult female northern elephant seals ( Mirounga angustirostris) to investigate age-related effects on diving performance. Blood volume averaged 74.4 +/- 17.0 L in female elephant seals or 20.2 +/- 2.0% of body mass. Plasma volume averaged 32.2 +/- 7.8 L or 8.7 +/- 0.7% of body mass. Absolute plasma volume and blood volume increased independently with mass and age. Hematocrit decreased weakly with mass but did not vary with age. Muscle myoglobin concentration, while higher than previously reported (7.4 +/- 0.7 g%), did not vary with mass or age. Pregnancy status did not influence blood volume. Mean dive duration, a proxy for physiological demand, increased as a function of how long seals had been at sea, followed by mass and hematocrit. Strong effects of female body mass (range: 218--600 kg) on dive duration that were independent of oxygen stores suggest that larger females had lower diving metabolic rates. A tendency for dives to exceed calculated aerobic limits occurred more frequently later in the at-sea migration. These data suggest that individual physiological state variables and condition interact to determine breath-hold ability, and that both should be considered in life-history studies of foraging behavior.
520 $a Chapter 2 identified both intrinsic state variables and extrinsic environmental variables that were found to influence foraging success through their impacts on behavior. In particular, I examined the extent to which intrinsic traits (mass and age) and extrinsic traits (year and season) impact diving and movement behavior. To do this, diving and satellite-tracked movement data were collected along with measures of mass and body composition from known-aged females at Ano Nuevo State Reserve, California. A principal component analysis reduced the dimensionality of movement behavior variables to three principal components that described time in foraging zones, foraging distances, and the structure of dives, respectively. Female mass was the only intrinsic variable to impact time in foraging zones, which described behavior relating to time diving and travelling to pelagic foraging habitat. Of the other principal components, foraging distances were impacted by yearly differences in the marine environment and dive structure was influenced by female age, but only during post-molt foraging trips when it had no measurable impact on foraging success. All principal components significantly impacted rates of energy gain, but only for the post-breeding foraging trip when maternal body stores are recovered under short time constraints before returning to shore for the molt fasting period. Bout characteristics of functional dive types showed qualitative support for the Marginal Value Theorem with increased energy gain resulting from higher proportions of patch residence time. Independent of age, female mass significantly influenced diving behavior in a way that positively influenced foraging success. This study links body mass to diving ability and foraging success, and provides a proximate mechanism for the cost of reproduction via reduced diving ability from mass lost to current offspring investment.
520 $a In Chapter 3, I studied trophic ecology of northern elephant seals in the ecological provinces of the North Pacific, combining satellite-tracking data and stable isotope analysis of vibrissae to evaluate variation in diet and potential impacts on foraging success. Telemetry data confirmed that offshore-nearshore differences in nitrogen availability establish clear gradients that make it possible distinguish individuals that forage in the California Current using stable isotope approaches. The California Current yielded higher delta 15N and delta13C values than all other regions, including the Alaska Downwelling province. Stronger differences in delta13 C gradients indicate that variation originates in 13C of organic sources at the base of the food web rather than differences in trophic structure across regions. Within the biogeographically distinct regions visited by northern elephant seals, individual delta13C and delta 15N values varied by as much as 2.0&permil; and 4.7&permil;, respectively. Within regions, isotopic values were highly variable among individuals, but mapped along a similar gradient as prey species. Linear mixed-effects models revealed strong effects of individual on isotopic composition, but no effects of age, body mass or related differences in the rate and magnitude of energy gain. A subsample of females satellite-tracked over multiple years exhibited strong route fidelity in all individuals, even when tracks were separated by more than a decade. Such fidelity reinforces strong regional gradients in delta13C, and to a lesser extent in delta15N, that resulted in lower isotopic values for females that foraged offshore. Wide variation among individuals within a region and strong route fidelity provide the first reported evidence for individual specialization in a highly pelagic predator.
590 $a School code: 0036.
650 4 $a Biology, Ecology. $3 1017726
650 4 $a Biology, Physiology. $3 1017816
690 $a 0329
690 $a 0719
710 2 $a University of California, Santa Cruz. $3 1018764
773 0 $t Dissertation Abstracts International $g 72-11B.
790 1 0 $a Costa, Daniel P., $e advisor
790 $a 0036
791 $a Ph.D.
792 $a 2011
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3471798